Time resolved atomic imaging – from seeing to measuring

The raise of nanoscience and nanotechnology and necessity to characterize the structure of individual objects consisting of countable number of atoms determined the shift of structure characterization paradigm from bulk methods like X-ray diffractometry to local high resolution methods like electron microscopy. The similar shift in paradigm is urging now in chemistry –chemical processes defining structure and properties of nanoscale and low dimensional objects often constitute a negligible part of the total volume of the material, and thus their assessment by bulk chemical methods if often impossible. The new concept is provided by the time resolved electron microscopy allowing for direct observation of atomic rearrangements.

We develop the methodology to apply the formalism and approaches of the classical chemical kinetics for the quantitative description of atomistic processes observable in the microscope. A proper statistical treatment of the data obtained in a range of experimental conditions allows determining of threshold energies for radiation induced reactions. But not only that: we show that true activation energies for thermally activated reaction pathways for individual defects can be estimated as well.

We apply this methodology for the experimentally simple cases: reactions of point defects in graphene. The cross-sections and threshold energies of irreversible (atom emission) and reversible (bond rotation) processes are determined. The values obtained reveal a few peculiar facts, some of them not having a clear physical explanation so far.

Institution: 

CIC nanoGUNE Consolider, San Sebastian, Spanien 

IKERBASQUE Basque Foundation for Science, Bilbao, Spanien

Date: 
Tuesday, September 5, 2017 - 11:00
Speaker: 
Prof. Andrey Chuvilin